This invention relates generally to energy storing devices, and more particularly, to an apparatus and method for treating a cathode material provided on a thin-film substrate.
The demand for new and improved electronic and electro-mechanical systems has placed increased pressure on the manufacturers of energy storing device to develop battery technologies that provide for high energy generation in a low-volume package. A number of advanced battery technologies have recently been developed, such as metal hydride (e.g., Nixe2x80x94MH), lithium-ion, and lithium polymer cell technologies, which would appear to provide the requisite level of energy production and safety margins for many commercial and consumer applications. Such advanced battery technologies, however, often exhibit characteristics that provide challenges for the manufacturers of advanced energy storage devices.
High-density, thin-film lithium batteries, for example, are typically fabricated using an anode comprising metallic lithium, lithium-metal alloy, lithium metal oxide or a lithium-carbon composite deposited on a substrate. In accordance with one battery configuration, the cathode comprises a metal oxide, typically a lithiated vanadium, or a modification of such an oxide, deposited on a metallic substrate. A solid polymer electrolyte film is typically situated between the active anode and cathode materials. Electrochemical cells, modules, and batteries may be fabricated using this basic anode/electrolyte/cathode thin-film laminate structure.
Manufacturers of high-density lithium batteries are currently faced with the challenge of producing reliable thin-film lithium cells within a high-volume manufacturing environment. A particular failure mechanism which has yet to be addressed and remedied in the prior art involves the instability of cell voltages which is often observed after forming thin-film electrochemical cells through use of a wrapping process. Another related failure mechanism involves the development of electrical shorts within the cells after completion of the wrapping process.
There is a need in the advanced battery manufacturing industry for a method and apparatus for fabricating high density, thin-film lithium cells and batteries which exhibit a reduced tendency for voltage instabilities and electrical shorts. The present invention fulfills these and other needs.
The present invention is directed to an apparatus and method for treating a cathode material provided on a surface of a thin-film substrate, and a treated thin-film cathode having increased smoothness. A web of untreated cathode material is moved between a feed mechanism and a take-up mechanism, and passed through a treatment station. The web of cathode material typically includes areas having surface defects, such as prominences extending from the surface of the cathode material. The surface of the cathode material is treated with an abrasive material to reduce the height of the prominences so as to increase an 85 degree gloss value of the material by at least approximately 10. The web of cathode material may he subjected to a subsequent abrasive treatment at the same or other treatment station. Burnishing or lapping film is employed at a treatment station to process the cathode material. An abrasive roller may alternatively be used to process the web of cathode material. The apparatus and method of the present invention may also be employed to treat the surface of a lithium anode foil so as to cleanse and reduce the roughness of the anode foil surface.
The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. Advantages and attainments, together with a more complete understanding of the invention, will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.